Palestinian security forces have clashed with protesters as they made their strongest effort yet to seal the volatile border between the Gaza Strip and Egypt. The Palestinians took action after Israel demanded a halt to weapons smuggling along the frontier.

Palestinian police fired in the air and clashed with stone throwing crowds on the Gaza border with Egypt. Police are trying to seal the chaotic frontier, after Palestinians tore down the border fence following Israel's pullout from Gaza last Monday. Since then, officials say, hundreds of assault rifles and pistols and thousands of bullets have been smuggled from Egypt to Palestinian militants in Gaza.

Israel is furious, because under a security agreement, Egypt deployed 750 troops along the Gaza border to prevent weapons smuggling. Israel has lodged a strong protest with both Egypt and the Palestinian Authority.

Zvi Mazel, a former Israeli ambassador to Egypt, says it's a grave situation that Israel cannot tolerate. "If we know and we see that passage and infiltration of terrorists continue, weapons smuggling continues, we should react, we will have to react, absolutely," he said.

Palestinian police have sealed five major breaches on the border, and the Egyptians have fortified their side with barbed wire. But the chaotic situation raises questions about whether the Palestinian Authority can restore law and order in turbulent Gaza, and control the heavily-armed militant groups that rule the streets.

It's an important test for Mr. Abbas. Israel has warned that if he fails, there will be no further concessions in the West Bank.